Novel oxidation catalyst compositions and processes



United States Patent Coyne, Prairie by mesne assignments, to GulfPittsburgh, Pa., a corporation of This invention relates to processes ofproviding unsaturated carbonylic compounds. More particularly, itrelates to processes of providing unsaturated carbonylic compounds bythe oxidation of olefins.

Compounds produced by the processes of this invention have well-knownutilities. For example, aldehydes such as acrolein and methacroleinprovided by processes of this invention are intermediates in producing anumber of other useful compounds. It is known in illustration thatacrolein can be employed as an intermediate in the production ofmethionine. It is further useful in the preparation of compounds such asthe resin intermediate hexanetriol, as a herbicide, and in a number ofpolymer applications in view of its alpha-unsaturation. Additionally,unsaturated aldehydes produced by the processes of thisinvention, suchas acrolein and methacrolein, can be converted by known processes totheir respective highly useful alkyl acrylic ester compounds. Also,those unsaturated ketones, Whichare oxidation products of certain of thehigher olefins, have utilities as solvents, as polym-. erizationmonomers, and the like.

By this invention are provided novel processes of producing unsaturatedcarbonylic compounds by the oxidation of an olefin having three to aboutten carbon atoms by contacting a gaseous stream of oxygen and saidolefin at an elevated oxidizing temperature with copper-sulfur oxygenoxidation catalyst complexes, also provided hereby, represented by thefollowing empirical formula:

a b c IZ d wherein M represents a silicon or a phosphorus atom; Nrepresents a molybdenum, vanadium, or a tungsten atom; and the lettersa, b, c, and d represent the amounts of the respective atoms as follows:a represents a number in the range from about one to about 20(preferablyfrom about five to about 15); b represents a number in therange from about 0.01 to about 10 (preferably from about 0.05 to aboutfive); c represents a number in the range from zero to about five(preferably from about 0.5 to about two, or up to about two); and d is anumber in the range from about 30 to about 100 (preferably from about 40to about 70). A further preferred catalyst has the empirical formula ofabout the following:

The metals of the catalyst complex are believed to be largely if notessentially totally in the form of their respec tive oxides. This isindicated by X-ray diffraction patterns and other data. However, it isnot meant to be bound by such theory or belief.

} The oxygen values recited are determined by calculation on basis ofthe oxygen content of oxides of the constituent metal atoms, assumingthey are fully present in the complexes as their respective oxides. Theassumed oxides as CuO, P 0 SiO S0 M00 W0 and V 0 A portion of additionalmetal atoms can be incorporated at times into the above defined catalystcomplexes without substantially hindering the oxidative processes.

Representative catalysts can be prepared as described hereinafter ingreater detail, by starting with a soluble copper salt (e.g., coppernitrate), a source of M and N atoms of the catalyst complex (e.g.,phosphomolybdic acid), and a source of sulfur such as sulfuric acid andammonium sulfate.

It is preferred in the processes of this invention to employ eitherpropylene or isobutylene, especially the latter. The oxidation of theseolefins provide the aldehydes, acrolein and methacrolein, respectively.However, other olefins having four or more carbon atoms, including,e.g., both alpha-olefins and beta-olefins can be oxidized to otherunsaturated carbonylic compounds, such as unsaturated ketones. Ethylvinyl ketone is an oxidation product of pentene-l and pentene-Z, whereasthe oxidation of alphaor beta-butylene provides methyl vinyl ketone.Furthermore, cyclopentenone-Z and methyl-isopropenyl ketone areoxidization products of cyclopentene and 2-met-hyl-butene-2,respectively.

Illustrative olefin compounds in addition to propylene and isobutylene,which are utilizable in the processes, include the following inillustration: propylene, butene-l, butene-Z, isobutylene, pentene-l,pentene-2, 3-methylbutene-l, Z-methyl-butene-Z, hexene-l, hexene-2,4-methyl-pentene-l, 3,3-dimethyl-butene-l, 4-methyl-pentene-2, octene-l,cyclopentene, cyclohexene, 3-methyl-cyclohexene, etc.

The catalyst employed in this invention can be prepared followingconventional procedures of catalyst preparation. For example, a generalprocedure found suitable in providing presently preferred catalystcomplexes of this invention, is as follows: Both the agent or agentsselected for use in the catalyst preparation to provide the M and Natoms (such as phosphomolybdic acid), a water-soluble copper compoundsuch as copper nitrate, and a suitable sulfur compound such as sulfuricacid are dissolved in a minimum volume of water. In the preparation, theminimum aqueous mixture can be added, and generally preferably is added,to a suitable support. For example, the aqueous mixture can be added toa heated silicon carbide aggregate in such a manner that the reagentswill coat or form a film on the aggregate particles. In forming thecoated aggregates, it is desirable that the aqueous mixture of thecatalyst source atoms be added to the heated aggregates at the same rateat which it is removed. The support suitably has about one to about tenpercent by weight of the catalyst complex, with usually three to abouteight percent desirable. The aggregate catalyst particles are suitablydried and fired in the usual manner as by heating to about 1000 F. Otheralternative procedures can be employed to provide suitable catalystpreparations and will be apparent to those skilled in the art from thedisclosures made herein.

Various suitable agents can be employed as sources of the atomconstituents of the catalyst complexes of this invention. Since presentevidence indicates the final activated catalysts, as used in the herebyprovided processes, contain the constituent metal atoms as a complex oftheir respective oxides, presumably the respective oxides couldtheoretically be employed as the starting materials. However, whether ornot the appropriate combination of the oxides of copper, silicon,molybdenum, sulfur, etc. could in fact be employed to provide a catalystof this convention, is not presently completely established.

In respect to copper, as mentioned above, water-soluble Salts of copperwhich are capable of disintegrating to the oxide of copper on firing thecatalyst but which do not leave an interfering residue have been foundsuitable as copper atom sources. Copper nitrate is a presently preferredsalt. Source agents for the M and N atoms include such agents asphosphomolybdic acid, molybdic acid, ammonium molybdate, phosphoricacid, polyphosphoric acid, silicomolybdic acid, phosphotungstic acid,tungstic acid, silicotungstic acid, phosphovanadic acid, silicovanadicacid, ammonium vanadate, and other suitable sources having adequatewater-solubility (the names of the acids are used in the sense of theirusual meanings to the chemical art). For a source of sulfur, any sulfurcompound can be used which has a suitable solubility and which is or canbe converted to its oxide on firing but again which does not on firingleave in the final catalyst complex a substantially interfering residue.Suitable sulfur source agents include sulfuric acid, ammonium sulfate,copper sulfate, and the like.

In respect to catalyst supports, silicon carbide is presently preferablebut other conventional supports which are inert in the processes of thisinvention can be employed. Such materials included silica gel,diatomaceous earth, certain clays, Alundum, alumina-silica, porcelain,alumina, titania, and the like. The support can vary widely in surfacearea, e.g., the support can have a high or low surface area. By lowsurface area is meant less than about five square meters of surface pergram of support, whereas by high surface area is meant more than aboutfive square meters of surface per gram of support.

Although it is preferred to employ a supported catalyst, it is withinthe scope of this invention to include the hereinabove named catalystcompositions in an unsupported form insofar as they catalyze theoxidation of olefins to desired carbonylic compounds.

The catalyst preparations, particularly the supported catalysts, aresubdivided if desirable as by crushing or grinding to provide a suitableparticle size for the processes. It has been found that a particle sizeof the catalyst is preferably of a size largely falling in a mesh rangeof about four to about 16 in the US. Sieve Series when a fixed bedtechnique is employed.

By employing processes of this invention, excellent conversions of theolefin are realized and, likewise, high yields of the desired carbonyliccompound or compounds are obtained. By yield of the carbonylic compoundis meant, in the usual sense, the percentage of the converted olefinobtained as the desired carbonylic compound. In illustration, if a 50percent of isobutylene feed is converted or consumed in a reaction andof the 50 percent converted isobutylene, 60 percent is in the form ofthe desired methacrolein, the yield then is 60 percent.

The processes of this invention are preferably conducted in a continuousmanner by passing the gaseous feed stream through an amount of thesupported catalyst in a fixed bed. In such an arrangement, conventionaloxidation apparatuses enabling a continuous procedure can be employed. Afluidized bed of catalyst can be used also. Even though the continuousprocedures are preferred, batch procedures and the like which willprovide the herein described oxidations are included within the scope ofthis invention.

The reaction temperature employed may vary considerably. The particularreaction temperature used depends upon the catalyst used, the olefinbeing oxidized, the flow rate of the gas feed, the contact time of theolefin with the catalysts, and other factors. In general, when operatingat pressures near atmospheric, temperatures in the range of about 350 toabout 650 C. are effective. A preferred temperature range in oxidationof isobutylene and propylene has been found to be about 400 to about 600C. The contact time of the olefin can vary considerably. Broadlyspeaking, it can vary from about 0.1 up to about 20 seconds. The optimumcontact time must be individually determined depending upon the ratio ofthe gas feed, reaction temperature, the olefin, the particular catalystemployed, and like factors. Generally, a 0.05 to about a five-secondcontact time is sufficient and is preferred.

A molar ratio of oxygen to olefin between about 5:1 to 0.511 (preferablyordinarily about 1:1) generally gives the most satisfactory results.Illustratively, in methacrolein preparation, a preferred ratio of oxygento olefin is about 1:1 on a volume basis. The oxygen used in the processmay be derived from any suitable source including, of course, oxygengas. However, air is a satisfactory source and is preferred in view ofeconomic considerations.

The addition of water to the olefin feed has been found to be highlydesired inasmuch as an improved conversion and yield of the desiredproduct is usually realized. Generally, a ratio of olefin to water inthe reaction mixture of 1:0.5 to 1:10 (by volume) will give satisfactoryresults. For example, a ratio of 1:1 to 1:5 has been found to be optimumwhen converting isobutylene to methacrolein. The water, of course, willbe in the vapor phase during the reaction. Therefore, an olefin feedhaving a ratio of olefinzoxygencwater of 1:0.5:0.5 to 1:5: 10 has beenfound suitable.

Inert diluents may be present in the feed without interfering with theoxidation. A much desired advantage of the processes of this inventionis the ability to oxidize, for example, isobutylene, in the presence ofother hydrocarbons, such as isobutane. This is an important qualitysince utilizable petroleum gas streams of isobutylene, for example,commonly contain a high percentage of saturated and other hydrocarbons.

In large scale operation, it is preferred to carry out the process in acontinuous manner. In commercial operations unreacted olefin often isrecovered and is recycled. The catalyst will require regeneration orreplacement from time to time.

The unsaturated carbonyl products can be suitably isolated from thereaction stream by any appropriate means. For example, the dischargestream can be passed through scrubbers containing water or otherappropriate solvents. The desired carbonylic compound can be recoveredfrom the scrubber solution by extraction, by distillation, or by otherconventional means. The efiiciency of the scrubbing operation may beimproved when water is employed as the scrubbing agent by adding asuitable wetting agent to the water. It is desired to include suitableinhibitors as is customary to prevent polymerization of the unsaturatedoxidation products.

The following illustrative examples are presented in illustration of theprocesses and catalyst compositions of this invention but not inlimitation thereof.

Example 1 A hot mixture of 13.0 g. of Cu(NO .3H O, 1.59 g. of ammoniumsulfate and 14.0 g. of phosphomolybdic acid in ml. of Water is addedwith stirring to 214 g. of a porous silicon carbide aggregate having a 4to 8 mesh size. The addition is carried on in such a manner that theevaporation of the water of the mixture is very rapid. The resulting dryparticles of catalyst are fired in an oven for two hours at 1000 F. Thedried catalyst is obtained in a yield of 230 g. and has about 7 percentby weight of the catalyst complex of the following formula: Cu S PMo O(empirical formulas given in examples determined by calculation).

The catalyst preparation can be repeated employing a high area catalystsupport, such as a high area silicon dioxide support.

A portion of the catalyst (200 ml.) is placed into a 400-ml. oxidationreactor. A feed stream vapor of isobutylene is employed having thefollowing composition by volume: isobutylene 13.6%; air 74.0%; andwater-12.4%. The reaction is conducted at approximately atmosphericpressure employing a temperature of 487 C. The contact time of themonomer feed with the catalyst bed is an average of 2.3 seconds. Theproduct is recovered in the customary manner employing water scrubbersand is analyzed by the Orsat and GLC methods (as used herein, GLC meansgas liquid chromatography). The conversion of isobutylene is 43 percentand the yield of methacrolein is 63 percent. 7

The process is repeated employing a 442 C. reaction temperature, anaverage contact time of 2.0 seconds, and a reaction feed having a ratioby volume (isobutylene:air:H O) of 13.7:75.6:10.7 to provide a 25'percent conversion of isobutylene and a yield of 57 percentmethacrolein.

The process is again repeated employing a 534 C. reaction temperature,an average contact time of 1.8 seconds, and a reaction feed having aratio by volume (isobutylenezairzH of 13.7 :75.'6:10.7 to provide a 44percent conversion of isobutylene and a 53 percent yield ofmethacrolein.

Example 2 A copper-phosphorus-molybdenum-sulfur catalyst complex isprepared by the procedure of Example I employing the same startingsilicon carbide aggregate support and the following reactants: 13.0 g.of Cu(NO .'3H O, 14.0 g. of phosphomolybdic acid, and 1.84 g. ofsulfuric acid. The empirical formula of the catalyst complex provided isCu S PMo O The dried supported catalyst has 7.4 percent by weight of thecatalyst complex.

The following results are obtained with the provided catalyst inrepeating the process of Example 1 and the indicated conditions: (1) 461C., 2.3 seconds contact time, and a ratio by volume -(isobutylenezairzH-O) of 13.6:74.0: 12.4 to provide a 40 percent conversion of isobutyleneand a 67 percent yield of methacrolein; (2) 488 C., 2.3 seconds contacttime, and a ratio of 13.6:74.0:12.4 to provide an isobutylene conversionof 41 percent and a methacrolein yield of 68 percent; (3) 466 C., 3.0seconds contact time, and a ratio of 13.1:71.2:15.7 to provide anisobutylene conversion of. 40 percent and a methacrolein yield of 66percent.

Example 3 (2) A copper sulfur phosphorus tungsten oxygen catalystcomplex is prepared using the following aqueous mixture: 24.1 g. ofphosphotungstic acid, 15.2 g. of Cu(NO .3H O, 1.44 g. of 95% H 80 and 65ml. of

water. Empirical formula:

(3) A copper-sulfur-silicon-tungsten-oxygen catalyst complex is preparedby using the following aqueous mixture: 23.9 g. of silicotungstic acid,15.2 g. of

1.44 g. of 95% sulfuric acid and 75 ml. of water. Empirical formula:

(4) A copper sulfur phosphorus vanadium-oxygen catalyst complex isprepared by using the following aqueous mixture: 20.5 g. of ammoniumphosphovanadate (prepared by the process described by A. Rosenheim andM. Pieck, Z. Anorg. Allgem. Chem. 98, 223-4916),

5 100 C. for eight hours.

6 28.3 g. of Cu (NO ".'3H' 0, 2.68 g.' of95%' sulfuric acid and 50 ml.of water. Empirical formula:

(5) A copper sulfur molybdenum oxygen catalyst complex is prepared byusing the following aqueous mixture: 20.4 g. of molybdic acid percent),21.7 g. of Cu(NO .3H O, 2.1 g. of sulfuric acid percent) and 60 ml. ofwater. Empirical formula:

(6) A copper-sulfur-tungsten-oxygen catalyst complex is prepared asfollows: tungstic acid (18 g.) is dissolved in 75 ml. of ammoniumhydroxide. The solution is added to 255 g. of commercially availablealuminum oxide having a low surface area sold by Carborundum Companyunder designation Grade AMC). The volatiles are evaporated and theparticles are coated by stirring. The partially coated carrier is heatedat 500 F. for one hour. After cooling, the alumina-tungstic acidparticles are treated with a solution containing 13 g. of

2.1 g. of sulfuric acid (95 percent) and 65 ml. of water. After removingthe volatiles under low heat, the catalyst is heat treated for two hoursat 1000 F. and cooled. Empirical formula:

(7) Si0 supported catalyst is made using: 2.1 g. of sulfuric acid (95percent), 22.9 g. of phosphomolybdic acid and 21.7 g. of Cu(N O .3H- Oare dissolved in 450 g. of 34% silica sol with heating and rapidstirring. The sol-catalyst mixture is heated (80 C.) and stirred until apermanent gel results. The catalyst gel is predried at The catalyst isthen heat treated for two hours at 1000 F. The catalyst particles arecrushed and the 4-16 mesh material is retained for oxidation. Empiricalformula of complex:

s z m sus These provided catalysts are employed in repeating theprocesses of Examples 1 and 2.

Other olefins such as propylene, pentene-l, butene-l, and Z-methylbutene-l, can be substituted as the olefin in the above specificallydescribed processes.

What is claimed is:

1. A process for converting isobutylene to methacrolein comprisingreacting isobutylene at a temperature within the range of about 400 C.to about 600 C. in the presence of oxygen, steam and a metal oxidecomposition consisting essentially of oxides of copper, sulfur,phosphorus and molybdenum, said oxides being present in the ratiosindicated, by the empirical formula the oxygen value of said empiricalformula being calculated, based on the assumption that the metal oxidesare fully present in the metal oxide composition as CuO, S0 P 0 and M00said metal oxide composition being on the surface of porous siliconcarbide aggregate.

2. A process according to claim 1 in which the metal oxide compositionhas the empirical formula 3. A process according to claim 1 in which themetal oxide composition has the empirical formula References CitedUNITED STATES PATENTS 1,955,829 4/1934 Pier et al 252-439 X 2,627,527 2/1953 Connolly et al. 260-604 (Other references on following page) 7UNITED STATES PATENTS Hadley 260-604 Bel1ringer et a1. 252- 435 XRobertson et a1 260597 Cheney et a1. 260-604 Romanousky et a1. 252-437Shotts et a1. 260-604 Callohan et a1. 252-437 Marullo et a1. 260597Johnson et a1 260604 8 FOREIGN PATENTS 6/1961 Belgium. 6/1960 GreatBritain.

5 LEON ZITVER, Primary Examiner.

LORRAINE A. WEINBERGER, Examiner.

MAURICE A. BRINDISI, R. H. LILES, H. T. CARTER,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,342,869 September 19, 1967 Roger P. Cahoy et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

line 10, for Cu S M0 0 read Cu S I Io O Column 6, 3 2

Signed and sealed this 15th day of October 1968.

(SEAL) Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

1. A PROCESS FOR CONVERTING ISOBUTYLENE TO METHACROLEIN COMPRISINGREACTING ISOBUTYLENE AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 400*C.TO ABOUT 600*C. IN THE PRESENCE OF OXYGEN, STEAM AND A METAL OXIDECOMPOSITION CONSISTING ESSENTIALLY OF OXIDES OF COPPER, SULFUR,PHOSPHORUS AND MOLYBDENUM, SAID OXIDES BEING PRESENT IN THE RATIOINDICATED, BY THE EMPIRICAL FORMULA